test: comprehensive coverage expansion for 1.9

Expand tests across three main areas:

1. **Host name/resolve tests** (10 new): auto-sequence naming,
   explicit override, whitespace rejection, UUID/name interchangeable
   lookup, suspend/resume/terminate via name, nonexistent error,
   resume-non-suspended no-op.

2. **Shared persistence suite** (14 new, shared by sqlite/postgres/
   in-memory): next_definition_sequence, get_workflow_instance_by_name,
   root_workflow_id round-trip, subscription token lifecycle, first
   open subscription, persist_workflow_with_subscriptions,
   mark_event_unprocessed, get_events filtering, batch
   get_workflow_instances, WorkflowNotFound, ensure_store_exists
   idempotency, execution pointer full round-trip, scheduled commands.
   Queue suite: 4 new. Lock suite: 3 new.

3. **Multi-step K8s integration test**: 4-step pipeline across 3
   different container images proving cross-image /workspace sharing
   through a SharedVolume PVC, bash shell override with pipefail +
   arrays, workflow.data env mapping, and output capture.

wfe-containerd/tests/integration.rs

@@ -68,6 +68,7 @@ fn make_context<'a>(
     pointer: &'a ExecutionPointer,
 ) -> StepExecutionContext<'a> {
     StepExecutionContext {
+        definition: None,
         item: None,
         execution_pointer: pointer,
         persistence_data: None,